1. Field of the Invention
The invention relates to processes for the manufacture of semiconductor devices and more particularly to the installation and qualification of processing equipment in a clean room facility.
2. Description of Prior Art
The fabrication of integrated circuit chips requires the use of extremely sophisticated and expensive processing equipment. A great many of these processing tools perform their chemical functions on silicon wafers through the use of a gaseous ambient and often require the use of high vacuum and reduced gas pressures. Machines with such diverse functions as chemical vapor deposition(CVD) tools, epitaxial reactors, sputtering tools, metal deposition evaporators, and plasma and reactive ion etching(RIE) tools all require the use of pumping packages which provide and high vacuum and gaseous ambient control.
The designers of semiconductor fabrication facilities necessarily concern themselves with the operation of these pumping stations, in particular with regards to the safe handling of gaseous discharges, noise, vibration, and general maintenance. Pumping equipment used for chamber evacuation and for maintaining flows of processing gases can be identified by two stages. The primary, or roughing stage involves mechanical pumps which have high pumping speed and capacity to preform the evacuation of process chambers from atmosphere down into the milliTorr range of pressure. This primary pumping equipment comprises large motor driven mechanical pumps which produce noise, vibration, and other undesirable disturbances to a clean room facility. They are best located in dedicated locations, apart from the locations of the tools which they service and are connected thereto by piping of appropriate size and construction. They can be contained in areas having a lower degree of cleanliness than that maintained for processing tools on the manufacturing floor. The pumping fluids used by these pumps are often attacked by corrosive elements in the gases resulting in pump damage and fluid deterioration. The pumps, therefore require frequent maintenance of a degree which would be disruptive to the manufacturing process, were they located in the same area as the tools themselves.
The secondary pumping stage, used when high vacuum is required, is typically accomplished by diffusion pumps which operate close to the processing chambers of the equipment they service and are non-mechanical in operation. These secondary pumps are part of the processing tool and are in turn backed up by the remote roughing pumps. Other types of "dry" mechanical pumps known as Roots blowers are sometimes used in series with oil based roughing pumps to achieve high pumping speeds.
An overall design and operation of a modern clean room facility for the fabrication of integrated circuits is dealt with by Wiemer et.al. U.S. Pat. No. 5,058,491. These authors provide for remote supporting equipment associated with integrated circuit fabrication tools to be located in a floor area below the clean room facility. They specify such equipment as motors, blowers, power supplies, heat exchangers, chemical transfer cabinets, etc. Roughing pump assemblies can also be located in such an area. Earlier clean room designs employed core areas which contained such support equipment and pumping stations and which located on the same floor level as the clean room areas and were isolated from the clean areas by a walled enclosure. Such single level fab designs are not as efficient and practical as the multi-level design outlined by Wiemer et.al. The multi-level facility lends itself particularly well to the maintenance of rough pumping equipment with minimal disturbance of the ongoing manufacturing process.
Suzuki et.al. U.S. Pat. No. 4,699,640 discuss the configuration of a clean room having areas of different degrees of cleanliness but do not discuss the installation and testing of pumping equipment or processing tools.
The installation, removal, or re-location of processing equipment is of significant concern to the efficient operation of a integrated circuit processing facility, Such operations come into play when older tools are replaced by newer ones, or when fab expansion or process redesign requires re-location or addition of processing tools. Conventionally, a processing tool is installed simultaneously with its support equipment. Such equipment includes electrical and cooling facilities, gas/air ventilation and exhaust facilities, operating gas supply, and primary vacuum pumping equipment. Simultaneous initial leak testing of the roughing pump assembly and the processing tool is not only disruptive to the ongoing clean area processing operations but is also potentially harmful to the processing tool itself. A simple example is backstreaming and damage to diffusion pumping fluids caused by fore line leaks.
The primary or rough pumping equipment, although custom configured for the tool it supports, can be acquired, installed, and qualified prior to the installation of the tool itself. Having the rough pumping equipment installed and tested ahead of time shortens the tool preparation time and greatly minimizes disruptions of process floor operations. It is this procedural sequence that is taught by this invention.